Phytoremediation experiments with Helianthus tuberosus under different pH and heavy metal soil concentrations

As results, soil pH and heavy metal concentrations were identified as crucial factors for plant growth and success of phytoremediation. High accumulation of Fe (up to 1.48 g/kg), Mn (up to 1.68 g/kg) and Zn (up to 853 mg/kg) was measured in the roots; shoots accumulated up to 2.6 g/kg Ni, 11.4 g/kg Mn and 6.06 g/kg Zn. The accumulation factors for the main heavy metals in the roots were determined. The heavy metal transfer factors Tf from roots to shoots for Ni, Zn and Mn were in the range of 11 to 15; hence the upper plant parts accumulated these metals more than the tenfold compared to the root concentrations. In contrast, heavy metal concentrations in tubers were reduced to 50% of Ni, 30% of Zn and Cu, 20% of Mn, 12% of Cd and 10% of Pb compared to the root contents. Fe, Cu and Pb were much less accumulated in the shoots, they mostly had been retained in the root system. The results also demonstrate the effects of specific transport, sequestration and protection mechanisms for each metal species in the plants. As results of the experiments, H. tuberosus represents a suitable and robust phytoremediation plant species for the phytoextraction of Mn, Zn, Cd and Ni under the given conditions from the site.